DESCRIPTION: ( Applicant's Abstract) Periodontal disease can be diagnosed in >50 percent of adults and may contribute to poor health through oral and systemic infection. The disease process is induced by bacteria and the severity of the disease seems due in large part to the immune response of the host. Over the past decades certain microorganisms have become highly implicated in the pathogenesis of periodontal disease including the gram negative Porphyromonas gingivalis (P. gingivalis). We have recently described and patented a small protein domain from P. gingivalis (HA2) that may be essential for the acquisition of iron and the porphyrin molecule, and, therefore, essential for survival of P. gingivalis in the periodontal pocket. Data indicated that the HA2 domain was detectable in clinical plaque samples and its detection was associated with hemoglobin binding activity within the plaque as well as with periodontal disease severity. Further, data indicated that an IgG humoral antibody response against the HA2 domain was stimulated with periodontal therapy and that this serum IgG could functionally inhibit hemoglobin-binding of the gingipains. These data implicate the HA2 domain of P. gingivalis as a good candidate for vaccine development to inhibit periodontal disease initiation and progression. PROPOSED COMMERCIAL APPLICATION: An effective vaccine against periodontal disease could be applicable to the entire population for the prevention of abatement of bone loss around the teeth that is often accompanied by acute abscess formation and loss of teeth. Notwithstanding malnourishment that accompanies partial or complete edentulism, periodontitis has significant untoward systemic effects so the value of this vaccine in terms of overall medical cost savings is enormous. Current treatment and prevention of periodontitis is ineffective or time-consuming and expensive.